Quick connect couplings have been widely used in the U.S. Automobile industry for many years. Although applicable in numerous applications, quick connectors are typically restricted to use in low-pressure applications such as fuel systems and vapor recovery systems. The simplest and most cost effective design is the plastic housing female type quick connector releasably mated to a metal male tube end form. The opposite end of the female housing most typically defines a stem having a number of axially spaced barbs formed on the outer circumferential surface thereof and a nylon or resilient plastic tubing end form pressed thereover. Such an arrangement is described in U.S. Pat. No. 5,542,712, issued Aug. 6, 1996, entitled "Quick Connector Housing With Elongated Barb Design".
Although suitable for use in their intended applications, the aforementioned connectors have been limited to relatively low pressure automotive applications. Designers of higher pressure systems such as air conditioning and engine cooling typically resort to traditional threaded type connectors which are constructed of relatively expensive screw machine formed components that, in application, require special tools for final assembly within the host system. In high volume automotive applications, the use of such labor intensive, expensive fittings are viewed as a distinct competitive disadvantage.
In fluid handling systems, it is imperative that the connectors used have their male and female portions properly coupled together. A faulty connector enables an associated system to leak fluid. This can be particularly disadvantageous when the system is under pressure and the leaking connector expels the pressurized fluid. Furthermore, recent Federal Legislation has mandated the elimination of certain refrigerants used in automotive air conditioning systems as well as significantly reduced the level of permissible emissions from automotive engine cooling and lubrication systems. Conventional quick connectors, although effective to mechanically maintain tubing end forms in assembly with their associated connector bodies, have not adequately addressed the federal requirements. Also, the materials employed, typically glass filed nylon, do not provide sufficient resistance to the permeation or seepage of refrigerant or coolants therethrough.
The female body portion of quick connectors are typically formed in one piece of injection molded thermoplastic or metal. Although generally configured in tubular form, the female body portion tends to have numerous complex contours and features which can prove difficult to form and assemble during the manufacturing process.
Another disadvantage inherent in many current quick connector designs resides in the necessity to fully assemble the connector prior to mating with a tube to form a fluid tight joint. A related shortcoming stems from the fact that typical quick connectors form a barbed nipple at one end for insertion within the I.D. of a very resilient (rubber or plastic) tube to establish a first relatively permanent joint. Thereafter, a second, relatively rigid, male member is received within an opposite opening within the female assembly and releasably engaged by a retainer. This results in two potential leak paths being introduced into the system. That is, at the interface between the exterior peripheral surface of the nipple and the I.D. of the resilient tube and a second leak path between the outer peripheral surface of the male member and the inner diameter of the mating through passage of the female connector body.
Finally, designers typically must compromise between high strength and design flexibility. Having both has historically resulted in complex and expensive configurations. A related problem stems from dual aspects of commercially available quick connect devices to wit; high volume and low sale prices frequently necessitating the use of inexpensive, somewhat pliable materials, and complex contours of extremely small inter-fitting components. These aspects collectively increase the likelihood of misassembly. High volume production techniques, including automated assembly tends to aggravate the problem wherein misassembly or impermissible dimensional variations of the components is difficult to detect. Excessive dimensional tolerance stack-up can result in low pull-apart characteristics between the barbed stem and the plastic tube to produce leakage. Misassembly, such as failure to include an O-ring can also result in leakage. Finally, plastic tube with low hoop strength can relax over time or at elevated temperatures, resulting in leaking or weeping of fluid.
A further disadvantage of typical prior art quick connector assemblies resides in the fact that they are intended to establish a joint between a first relatively rigid (typically metal) tube end form and a second resilient (typically rubber or vinyl) tube end form. Such connectors are typically unsuitable for coupling two rigid (metal or hard plastic) tube end forms. Lastly, in the case of electrically conductive tube material, prior art quick connectors typically do not provide a reliable path of electrical conductivity through the connector.